Contents transmitted into a home via the Internet is usually sent to a personal computer. Compression music data, image data, and the like which were downloaded are stored into the personal computer. The user tries to reproduce those contents which arrived at the personal computer by an AV (audio and/or visual) apparatus other than the personal computer. However, if a network in the home does not exist, it is difficult to realize such a request.
As network architectures, an Internet protocol system called TCP/IP (Transmission Control Protocol/Internet Protocol) used in the Internet and an OSI (Open System Interface) basic reference model have been known. The OSI reference model comprises seven layers. The first layer is a physical layer. The second layer is a data link layer. The third layer is a network layer. The fourth layer is a transport layer. The fifth layer is a session layer. The sixth layer is a presentation layer. The seventh layer is an application layer. In the physical layer, a physical mutual connection is made. Data is handled as a bit train here. In the data link layer, a physical communication path to a communication partner is assured and a competition control or the like is performed. Data is handled here as a unit such as a frame or the like which has been more structured.
The TCP/IP comprises four concept layers: a network interface layer, an Internet layer, a transport layer, and an application layer. Those layers are constructed on the physical layer. They can be made to correspond to those of the OSI reference model as follows: the data link layer→the network interface layer; the network layer→the Internet layer; the transport layer→the transport layer; the session layer, presentation layer, application layer→the application layer. The network interface layer is a layer for assuring communication in one subnetwork. For example, a PPP (Point-to-Point Protocol) for making communication between two points corresponds to the network interface layer.
The PPP (Point-to-Point Protocol) is a protocol which is used as a standard protocol by a dial-up IP connection. Data communication by a plurality of protocol authentication is provided by a line which is connected in a one-to-one correspondence relation. As a connecting procedure, a link is established via 1) a link establishing request, 2) authentication of a connecting person, and 3) an information exchange of every protocol.
As networks in the home, wire transmission systems such as IEEE (Institute of Electrical and Electronics Engineers) 1394, Ethernet, and the like, and several wireless transmission systems have been proposed. As wireless transmission systems, IEEE802.11, Bluetooth (trademark), Wireless1394, and the like have been proposed. The networks in the home according to those various transmission systems construct an LAN (Local Area Network).
In recent years, the number of terminal apparatuses which are connected to the network in the home has been increasing. Each terminal apparatus is not limited to communication which is merely made to a specific target but is also connected to the Internet and can be also referred to from a network over the LAN. In order to allow the terminal apparatus to participate in such a network, there is needed a terminal apparatus called a router for at least allowing information to pass from one LAN to another LAN and enabling an information exchange with another terminal apparatus in the network to which the relevant terminal apparatus has been connected.
Although the setting of routing of the router is performed by the user, since the setting operation is technical and expert, when the user newly connects a terminal apparatus, it is necessary to execute the troublesome setting operation.
The foregoing general network architecture, for example, the TCP/IP protocol is also applied to the homenetwork. In the case where the homenetwork is a wireless network, in order to prevent the third person from looking surreptitiously, it is desirable to perform an authentication encryption at the level of the data link layer. Since the setting operation of the router having the wireless data link for such a purpose is technical and expert, when the user newly connects a terminal apparatus, it is necessary to execute the troublesome setting operation.
Further, from a point of protection of personal information, it is demanded that the homenetwork is a secure network. Hitherto, a firewall has been provided between the public network and the private network. This is because it is intended to prevent a person called a cracker who invade illegally the network. However, such a homenetwork depends on the provided firewall and the homenetwork does not become open, so that there is a problem such that it becomes an obstacle in case of developing a variety of kinds of applications.
It is, therefore, the first object of the invention is to provide a network system for enabling the user to easily connect a terminal apparatus to a router.
The second object of the invention is to provide a network system for enabling authentication at a data link level although the setting operation of a router having a wireless data link is unnecessary.
The third object of the invention is to provide a network system which can construct a secure network without providing a firewall.